The present invention relates to apparatus for imprinting an elongated member, and more particularly to such apparatus having a circumferentially grooved-rim printing wheel toward which an ink jet is aimed, the aperture angle of the jet being within the edges of the printing wheel rim, while an ink wiper bears against the printing wheel in opposition to its direction of rotation.
In printing devices that are currently available on the market, the printing wheel dips into an ink bath, or sometimes a wide-angle inking jet is used in place of the immersion tank. For adequate printing quality, the known devices of this kind are limited to operating speeds of about 400 m/min. The large wipers used up to now, which wipe off the ink spilled over the sides of the wheel as well as the excess ink in the concave groove of the printing wheel, act as a brake on the printing wheel, which is driven by frictional contact with the member to be imprinted in the so-called "wire drag" mode. At operating speeds above 400 m/min, this braking action often causes slippage between the elongated member and the wheel, resulting in an objectionably smeared pattern. Even the use of special inks could not remedy this situation.
U.S. Pat. No. 2,934,005, issued Apr. 26, 1960 to J. C. Gemelli, describes printing apparatus of this general type, and its disclosure is incorporated herein by reference. In the design of this patent, the printing wheels rotate on vertical axes. However, this device permits production speeds of only up to about 900 m/min. Alternatively, there have been attempts to get higher printing speeds through electronically controlled drives, but without success.